1. Field of the Invention
This invention relates to structures of thin film magnetic write heads. More specifically, the invention relates to structures of a thin film write heads for thermally assisted magnetic recording, wherein an optical aperture serving as ridge waveguide near field optical source is integrated with heat sinking components situated at the air bearing surface.
2. Description of the Related Art
The ongoing quest for higher storage bit densities in magnetic media used in, for example, hard disk drives, have reduced the size (volume) of data cells to the point where the cell dimensions are limited by the grain size of the magnetic material. Although grain size can be reduced further, there is concern that data stored within the cells is no longer thermally stable, as random thermal fluctuations at ambient temperatures are sufficient to erase data. This state is described as the superparamagnetic limit, which determines the maximum theoretical storage density for a given magnetic media. This limit may be raised by increasing the coercivity of the magnetic media or lowering the temperature. Lowering the temperature is not a practical option when designing hard disk drives for commercial and consumer use. Raising the coercivity is a practical solution, but requires write heads employing higher magnetic moment materials, or techniques such as perpendicular recording (or both).
One additional solution has been proposed, which employs heat to lower the effective coercivity of a localized region on the magnetic media surface; writes data within this heated region with a broad magnetic field; and, “fixes” the data state by cooling the media to ambient temperatures. This technique is broadly referred to as “thermally assisted (magnetic) recording”, TAR or TAMR. Heat is applied to a magnetic substrate via a very small, but intense light source to reduce the anisotropy of fine grain magnetic media. A potential advantage is that lower field gradients produced by heads having broader field dimensions may be used, which relaxes the tight dimensional requirements of the magnetic source or write head. It can be applied to both longitudinal or perpendicular recording systems, although the highest density state of the art storage systems are more likely to be perpendicular recording systems. Heating of the media surface is accomplished by a number of techniques such as focused laser beams or near field optical sources. To be useful for high density recording, the light source utilized for heating must be on the order of 50 nm or less in diameter. This is far beyond the optical diffraction limit for conventional light sources such as solid state lasers, which leaves near field optical sources as the preferred heating method.
One method that commonly used to produce near-field light is the ridge aperture or “C” shaped aperture. The device consists of rectangular shaped aperture fashioned in an electrically conductive metal film. Extending into the center portion of the aperture is an electrically conductive ridge, generally an extension of the surrounding metal film. Incident radiation, polarized in the direction parallel to the ridge produces an intense pattern of near-field light which appears close to or at the end of the ridge, in the gap between the end of the ridge and the opposing boundary of the aperture.
While the near field light source is positioned to induce heating in the magnetic media, a certain percentage of heat will also be generated in the magnetic head, particularly in the vicinity of the ridge aperture. This heating can affect the shape of the head at the ABS, and therefore impact the fly height. Heating of the head can also impact the reliability and performance of the head because high temperatures can accelerate thermal migration of various films and structures, causing inter-diffusion and dimensional smearing. Therefore it may be necessary to dissipate excessive heat created by the near field light source and radiated to the magnetic head by providing appropriate heat sinking.
What is needed is an improved method for thermally assisted recording.